// sha3.c
// 19-Nov-11  Markku-Juhani O. Saarinen <mjos@iki.fi>

// Revised 07-Aug-15 to match with official release of FIPS PUB 202 "SHA3"
// Revised 03-Sep-15 for portability + OpenSSL - style API

#include "common/sha3.h"

// update the state with given number of rounds

void
sha3_keccakf(uint64_t st[25]) {
  // constants
  const uint64_t keccakf_rndc[24] = {
      0x0000000000000001, 0x0000000000008082, 0x800000000000808a,
      0x8000000080008000, 0x000000000000808b, 0x0000000080000001,
      0x8000000080008081, 0x8000000000008009, 0x000000000000008a,
      0x0000000000000088, 0x0000000080008009, 0x000000008000000a,
      0x000000008000808b, 0x800000000000008b, 0x8000000000008089,
      0x8000000000008003, 0x8000000000008002, 0x8000000000000080,
      0x000000000000800a, 0x800000008000000a, 0x8000000080008081,
      0x8000000000008080, 0x0000000080000001, 0x8000000080008008};
  const int keccakf_rotc[24] = {1,  3,  6,  10, 15, 21, 28, 36, 45, 55, 2,  14,
                                27, 41, 56, 8,  25, 43, 62, 18, 39, 61, 20, 44};
  const int keccakf_piln[24] = {10, 7,  11, 17, 18, 3, 5,  16, 8,  21, 24, 4,
                                15, 23, 19, 13, 12, 2, 20, 14, 22, 9,  6,  1};

  // variables
  int i, j, r;
  uint64_t t, bc[5];

#if __BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__
  uint8_t* v;

  // endianess conversion. this is redundant on little-endian targets
  for (i = 0; i < 25; i++) {
    v     = (uint8_t*)&st[i];
    st[i] = ((uint64_t)v[0]) | (((uint64_t)v[1]) << 8) |
            (((uint64_t)v[2]) << 16) | (((uint64_t)v[3]) << 24) |
            (((uint64_t)v[4]) << 32) | (((uint64_t)v[5]) << 40) |
            (((uint64_t)v[6]) << 48) | (((uint64_t)v[7]) << 56);
  }
#endif

  // actual iteration
  for (r = 0; r < KECCAKF_ROUNDS; r++) {
    // Theta
    for (i = 0; i < 5; i++)
      bc[i] = st[i] ^ st[i + 5] ^ st[i + 10] ^ st[i + 15] ^ st[i + 20];

    for (i = 0; i < 5; i++) {
      t = bc[(i + 4) % 5] ^ ROTL64(bc[(i + 1) % 5], 1);
      for (j = 0; j < 25; j += 5) st[j + i] ^= t;
    }

    // Rho Pi
    t = st[1];
    for (i = 0; i < 24; i++) {
      j     = keccakf_piln[i];
      bc[0] = st[j];
      st[j] = ROTL64(t, keccakf_rotc[i]);
      t     = bc[0];
    }

    //  Chi
    for (j = 0; j < 25; j += 5) {
      for (i = 0; i < 5; i++) bc[i] = st[j + i];
      for (i = 0; i < 5; i++) st[j + i] ^= (~bc[(i + 1) % 5]) & bc[(i + 2) % 5];
    }

    //  Iota
    st[0] ^= keccakf_rndc[r];
  }

#if __BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__
  // endianess conversion. this is redundant on little-endian targets
  for (i = 0; i < 25; i++) {
    v    = (uint8_t*)&st[i];
    t    = st[i];
    v[0] = t & 0xFF;
    v[1] = (t >> 8) & 0xFF;
    v[2] = (t >> 16) & 0xFF;
    v[3] = (t >> 24) & 0xFF;
    v[4] = (t >> 32) & 0xFF;
    v[5] = (t >> 40) & 0xFF;
    v[6] = (t >> 48) & 0xFF;
    v[7] = (t >> 56) & 0xFF;
  }
#endif
}

// Initialize the context for SHA3

int
sha3_init(sha3_ctx_t* c, int mdlen) {
  int i;

  for (i = 0; i < 25; i++) c->st.q[i] = 0;
  c->mdlen = mdlen;
  c->rsiz  = 200 - 2 * mdlen;
  c->pt    = 0;

  return 1;
}

// update state with more data

int
sha3_update(sha3_ctx_t* c, const void* data, size_t len) {
  size_t i;
  int j;

  j = c->pt;
  for (i = 0; i < len; i++) {
    c->st.b[j++] ^= ((const uint8_t*)data)[i];
    if (j >= c->rsiz) {
      sha3_keccakf(c->st.q);
      j = 0;
    }
  }
  c->pt = j;

  return 1;
}

// finalize and output a hash

int
sha3_final(void* md, sha3_ctx_t* c) {
  int i;

  c->st.b[c->pt] ^= 0x06;
  c->st.b[c->rsiz - 1] ^= 0x80;
  sha3_keccakf(c->st.q);

  for (i = 0; i < c->mdlen; i++) {
    ((uint8_t*)md)[i] = c->st.b[i];
  }

  return 1;
}

// compute a SHA-3 hash (md) of given byte length from "in"

void*
sha3(const void* in, size_t inlen, void* md, int mdlen) {
  sha3_ctx_t sha3;

  sha3_init(&sha3, mdlen);
  sha3_update(&sha3, in, inlen);
  sha3_final(md, &sha3);

  return md;
}
